This invention relates generally to systems for producing injection molded articles, and more particularly, to an arrangement and method of forming internally ribbed injection molded articles whereby material usage is minimized and manufacturing speed is improved.
It is generally desired in certain injection molded articles, such as display frames of the type which are used for pictures, cards, and other items, that an aesthetically pleasing dimensioning and configuration be maintained to achieve a desired decorative appearance. Generally, such a desired decorative appearance is achieved, illustratively in the display frame art, by providing a relatively large frame thickness such that a somewhat massive appearance is produced. Display frames of the type which are produced by conventional injection molding systems achieve the desired massive appearance by using large amounts of molding material.
It is a problem with a conventional frame that the polymeric or other molding materials are expensive. Of equal importance, however, is the fact that when a massive injection molded article is solidifying, a surface irregularity is produced caused by internal shrinkage of the mold material. This results in a condition known as "sink" whereby the central region of a surface is depressed inwardly. In addition to the high cost and surface irregularities of massive injection molded articles, such articles are plagued by the further problem that their manufacture proceeds at a relatively slow rate. This is caused by the fact that a relatively long solidification period is required before the article can be removed from the mold. In essence, a relatively long machine cycle is required for producing massive injection molded articles.
The prior art has thrust at the problems associated with massive injection molded articles by creating a product having an internally ribbed appearance. Generally, the formation of internal ribs required additional machining operations after molding was completed. Thus, although some molding material was salvaged by such post-molding machining, this technique did not eliminate the problem of surface sink. Additionally, the subsequent machining of a massive injection molded article does not solve the problem of extended machine cycle times. Thus, the conventional approach to producing internally ribbed articles, such as display frames, is expensive and complex.
It is, therefore, an object of this invention to provide a simple and inexpensive molding system. It is another object of this invention to provide a simple and inexpensive molding system which is suitable for injection molding.
It is also an object of this invention to provide a mold arrangement for manufacturing injection molded products which are not subject to surface sink defects.
It is a further object of this invention to provide a mold system for producing internally ribbed products whereby aesthetic and decorative dimensions are maintained and a substantial reduction in the usage of molding material is attained.
It is additionally an object of this invention to provide a mold system for producing injection molded display frames.
It is also another object of this invention to provide a mold system for manufacturing display frames having decoratively large face width dimensions, while minimizing consumption of the molding material.
It is a yet further object of this invention to provide a mold arrangement for producing display frames which are internally ribbed longitudinally along respective sides thereof.
It is also an additional object of this invention to reduce the time required to manufacture an injection molded article.
It is still another object of this invention to reduce machine cycle times in the injection molding manufacture of articles.
It is a still further object of this invention to improve the efficiency with which an article is removed from an injection mold system.
It is yet another object of this invention to provide an injection mold for an internally ribbed frame member wherein the frame member is easily removed from the mold.
It is additionally a further object of this invention to provide an injection mold system for a display frame which does not require a mold core dedicated exclusively to the forming of a slot through the display frame.